From: Nathan Smith (stryyker_at_keypoint.com.au)
Date: 2003-12-02 03:37:31
----- Original Message ----- From: "Brian Ketterling" <firstname.lastname@example.org> To: <email@example.com> Sent: Tuesday, December 02, 2003 12:51 PM Subject: Re: Assemblers for the 65816 processor > Hi -- > > By the way, I have a question about SCPU RAM that Maurice Randall couldn't > help me with. There's that page of "user" RAM in the $Dxxx(?) area, which I > thought might be handy for an alternative zero page or something. However, > CMD advised that if you want to write to it, which requires enabling the > hardware registers, you should do so and then slam the lid shut again as > fast as possible. If your program doesn't write to the shadow registers, > why is this necessary? It *seems* overly cautious. > > Also, if I may say... that little booklet that comes with the SCPU is pretty > pathetic. The SCPU could REALLY use a P.R.G., I think. > > -- Brian > From memory it is $d3xx (or was it $D2xx?) so it uses what C64 normally mirrors the VIC to. I guess you do it quickly so no accidental writes. There may be some IO reasons too which the CPLD addresses. I do agree a nice reference would be nice. So many of the registers are not documented even if they are not supposed to be used. Anyone checked how well the IO mapping is handled for stack is moved there? It always writes to RAM? Movable stack is something very useful missing from 6502/6510, imagine bytes and cycles saved. Message was sent through the cbm-hackers mailing list
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